Method for the preparation of seized metal-stranded cable



Sept. 15 1 59 c. E. ROBERTS Em 2,903,843

METHOD FOR THE PREPARATION OF SEIZED METAL-STRANDED CABLE Filed Oct. 1, 1957 v 2 Sheets-Sheet 1 INVENTORS i CARL EMERSON ROBERTS JAMES PERSH/NG SW50;

Sept. 15, 1959 c. E. ROBERTS ETAL 2,903,843

METHOD FOR THE PREPARATION OF SEIZED METAL-STRANDED CABLE Filed Oct. 1, 1957 2 Sheets-Sheet 2 INVENTORS CARL EMERSON ROBERTS JAMES PERSHING SWED ATTORNEY United States Patent METHOD FOR THE PREPARATION OF SEIZED lVIETAL-STRANDED CABLE Carl Emerson Roberts, Pompton Lakes, and James Pershing Swed, Gibbstown, N.J., assignors to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware Application October 1, 1957, Serial No. 687,581

9 Claims. (Cl. 57-460) The present invention relates to seized metal-stranded cable and to a method for the preparation of such cable. More particularly, the present invention relates to metalstranded cable having a portion thereof seized by explosive means.

Metal-stranded cable, for example wire rope, is used in a wide variety of applications, such as in the drilling of wells and the like and in slings, hoists, cranes, and so forth. Many of these applications require the cutting of the cable. In such operations, difficulties have been encountered in that the strands of the cable unravel either during the cutting operation or thereafter. As a result, such sections of the cable are difficult to handle. Moreover, when the unraveling occurs during the cutting operation, this operation is hampered since the strands catch in the saw teeth and bend or break the blades.

Many methods have been used in efforts to prevent this unraveling. One of these methods involves the fusing together of the cut strands, for example by the use of heat-producing electric cutters. However, very frequently the cable must be cut in the field, where use of such cutters is not feasible. Various forms of cable seizing, that is,-the binding of a section of the cable with an exten'or supporting member, also have been used in attempts to overcome this problem. A wrapping of tape, e.g. adhesive tape, or of wire provides a very satisfactory seize on very small-diameter cables, i.e. of less than inch in diameter, which can be cut with wire cutters or the like. However, the tape or wire is unsatisfactory when applied to larger-diameter cable, which must be cut with a hacksaw or the like, because during the cutting operation the sawing action pulls the tape or wire from the cable, and, thus, unraveling of the strands occurs and the unraveled strands catch in the saw teeth. In many instances, constriction of a metal sleeve about the cable provides an adequate seize, but this method has several inherent disadvantages. For example, the equipment required for this operation not only is very expensive but also is not suitable for field use. In addition, the sleeve must he slipped over the end of the cable and down its length, sometimes down hundreds of feet of cable, to the section which is to be seized. Obviously, the thereby necessitated handling of hundreds of feet to cable is highly disadvantageous, and, moreover, in some cases, the end of the cable over which the sleeve must be passed is not available, e.g. when fittings are fastened to the ends. Furthermore, the presence of the sleeve increases the diameter of the seized portion of the cable, and in certain applications of the cable, such increase in diameter cannot be tolerated, e.g. when the cable has to be drawn through tubing or fixtures of inner diameter approximately equal to the normal diameter of the cable.

Accordingly, an object of the present invention is to provide seized metal-stranded cable prepared by a simple and inexpensive method. Another object of the present invention is to provide seized metal-stranded cable and a method for the preparation thereof which method is suitable for use in the field. A further object of the 2,903,843 Patented Sept. 15, 1959 present invention is to provide a convenient method of seizing metal-stranded cable which seized cable is suitable for use in all applications of metal-stranded cable.

We havev found that the foregoing objects may be achieved when we wrap thin metal sheeting around the portion of the cable to be seized and subject the wrapping to the pressures generated by the detonation of an explosive.

In accordance with the present invention, the portion of the cable to be seized is surrounded by a wrapping of flexible metal sheeting, preferably 5-35 mils in thickness, the wrapping is substantially completely surrounded by a charge of a detonating explosive, and the explosive is initiated. Surprisingly, We have found that when a thin metal wrapping surrounding a portion of metal-stranded cable is explosively constricted in accordance with the method of the present invention, the thin metal provides suflicient holding strength to-permit the mechanical working, e.g. cutting, of the seized portion without the unraveling of the cable and yet the diameter of the cable in the region of the seize is not substantially altered. As may be seen by reference to the accompanying Figures 1 and 2, drawings of the seized metal-stranded cable and of such cable after cutting, respectively, the thin metal is forced tightly into the lay of the cable in a manner such that substantially no change occurs in the diameter of the seized portion, the presence of the thin metal wrapping having negligible effect on the diameter of the cable. a

Reference is made to the accompanying drawings presented in order to describe more fully the nature of the present invention and in which:

Figure 1 represents a length of cable having a seized portion and Figure 2 represents the same cable severed at the seized portion.

Figure 3 represents one embodiment of the wrapping of the present invention, and Figures 4-6 illustrate additional embodiments of the wrapping of the present invention.

In Figures 1 and 2, 1 represents a strip of metal sheathing and 8 represents metal cable. The strip of metal sheathing 1 hasbeen wrapped around cable 8 as indicated in Figure 1, and forced into the lay of cable 8 in accordance with the method of the present invention. The cable 8 was then cut by means of a hacksaw through the portion covered by strip 1.

Referring now to Figures 3-6 in greater detail, in each case 1 indicates a strip of flexible metal sheeting, preferably 5-35 mils in thickness. In Figure 3 is shown an embodiment in which perforations indicated by 2 are formed in the sheeting. In the embodiment illustrated in Figure 4, 3 represents one end of the sheeting bent back or rolled to form a hook which interlocks with the oppositely directed hook 3A formed at the other end of the sheet by bending or rolling, both ends of the sheet preferably being cut diagonally prior to formation of the hooks.

In Figure 5, 4 indicates a series of parallel prongs cut into one end of the sheet '1, the prongs 4 interlocking with the corresponding slots formed in the other end of the sheet and indicated by 5. In the embodiment shown in Figure 6', one end of the sheet 1 is tapered to form a narrow projection 6 which interconnects with one of a series of slits 7 formed in the other end of the sheet.

' As is obvious, all of the above-mentioned embodiments of the wrapping, as well as many other variations including a plain band of sheet metal, may be cut to fit and formed according to the desired modification in the field. Therefore, costly pre-forming of the wrapping is not required and sheet metal available at the place of operations can be used. i

The following examples serve to illustrate specific embodiments of the cable-seizing method of the present invention. However, they will be understood to be illustrative only and not as limiting the invention in any manner.

Example 1 A strip of copper sheeting 17 mils in thickness and about 6 inches in length and 1 inch in width was perforated to give /a-inch holes, one every /2 inch, three rows of the holes being provided as shown in Figure 3. The perforated strip was wrapped lengthwise around a l-inch-long section of %-inch-diameter steel cable, about 2 layers of the wrapping being formed. A fii-inch-thick layer of neoprene was positioned around and over-lapped slightly the wrapping, and then a length QfSO-gr'ainerfoot PETN detonating cord (Primacord manufactured by the Ensign-Bickford'Co.) was Wrapped around the neoprene in a manner such that the cord substantially surrounded the neoprene (four turns of the cord). An electric blasting cap was attached to one end of the cord and then was actuated. 'Ihe detonation of the cord re? sulted in the blowing apart of the rubber cushion and the forcing of the metal strip into the lay of the cable to give a good seize, the driving of the copper sheeting into the perforations providing additional gripping action.

Example 2 The procedure of Example 1 wasrepeated with the exception that the metal strip illustrated in Figure 6 was substituted for the perforated strip. The slits in the strip were /2 inch long by /8 inch wide, and the tapered end of the strip 'was tucked into one of them. Again, a good seize was obtained.

Example 3 The ends of a strip of aluminum sheeting mils thick and 1 inch wide were diagonally cut at an angle of 45 to form parallel ends which were bent back into hooks as shown in Figure 4. Each hook was inch in width, and the over-all length of the resultant strip was about 3 inches. The strip was wrapped lengthwise around a l-inch-long section of A-inch-diameter steel cable, and the books were interlocked and pressed flat, the wrapping fitting snugly around the cable. A 25-inch length of explosive connecting cord containing 2 grains of PETN per foot of length was wrapped around the aluminum strip and was initiated by an electric blasting cap attached to one end of the cord. Upon detonation of the cord, a good seize was obtained, which was cut through by means of a hacksaw into 2 sections as shown in Figure 2.

Example 4 A strip of steel sheeting 15 mils in thickness, about 1 inch wide, and slightly over 4 inches in length was formed into the configuration shown in Figure 5. The strip was wrapped lengthwise around a one-inch-long section of lMz-inch-diameter steel cable, and the prongs were interconnected with the corresponding slots. The wrapping was substantially surrounded by 5.5-grain-per-foot PETN explosive connecting cord, which then was actuated by an electric blasting cap, and a good seize was obtained.

As may 'be seen by reference to the foregoing examples, very satisfactory, seized metal-stranded cable is obtained easily when a wrapping of thin metal sheeting is provided around the section of the cable to be seized and is constricted by the pressures generated by the detonation of an explosive charge surrounding the wrapping. Although only very thin and workable metal sheeting is wrapped and constricted around the cable, the forcing of the wrapping into the lay of the cable apparently imparts sufiicient holding strength to the wrapping that the seized portion can be readily cut. Furthermore, we have foundthis method to be an effective and advantageous way of completing a wire splice, i.e. the connection of two lengths of metal-stranded cable by the interweaving of the strands of the adjacent ends of the two lengths. In

.4 wire splicing, the loose ends of the strands protrude from the spliced section of the cable and frequently interfere with its use by snagging or catching onto other objects, for example, pulleys and the like. However, by seizing the spliced section, in accordance with the method of the present invention, at the points at which these loose ends protrude, the ends are held down and a smooth splice results.

The seizing method of the present invention is generally applicable for all types and sizes of metal-stranded cable. However, the seizing of cable smaller than that of about inch in diameter is impractical because cable of such diameter can be cut readily when bound by a length of tape or by wire or even when unseized.

The explosive charge used in the method of the present invention is of the detonating type, the specific composition of the explosive not being critical. The amount of the explosive used is dependent upon such variables as the diameter of the cable, the thickness of the wrapping, the material of the wrapping, and the strength and shattering action of the explosive composition. The minimum amount of explosive which can be used is that amount which will propagate its detonation when spread over the surface of the wrapping. When explosive compositions having a great deal of shattering action are used, the imposition of a layer of modifying material between the explosive charge and the wrapping, as illustrated in Examples 1 and 2, is desirable, in order to modify the forces of the detonation and thereby prevent shattering of the wrapping. The modifying material may be the exemplified rubber or one of a wide variety of yielding mate: rials including plastics, paper and fibers, among others.

The exact configuration of the explosive charge is not critical, the only requirement being that the charge substantially surround the wrapping. Because of their ready availability and ease of handling, the cord-type explosives were used in the experiments described in the examples. However, the use of other explosive configurations is equally feasible and within the scope of the present invention. For example, a sheet of PETN or RDX or the like could be substituted for the detonating cord of the examples, and equivalent results would be obtained. We have found the explosive connecting cord of Examples 3 and 4, which cord comprises a metal sheath containing 0.1 .to 10 grains of a high-velocity detonating explosive per foot of sheath length and is described in detail in a pending application, Serial No. 597,145, filed July 11, 1956, and now abandoned, by D. J. Andrew, R. W. Felch, and G. A. Noddin and assigned to the present assignee, to be highly satisfactory and, thus, its use constitutes a preferred embodiment of the invention.

The metal sheeting used as the wrapping preferably is 5 to 35 mils in thickness, since metal sheeting of such thiclcness is flexible enough to be wrapped easily around the cable and is strong enough that itwill not tear during this operation. Suitable metals include copper, aluminum, steel, etc. Plain metal sheeting of the desired width and length may be simply wrapped around the cable, one or more layers of the wrapping being provided, or, in some cases, metal strips provided with fastening means may be used. Such strips would include the configurations shown in Figures 4-6 and, obviously, other variations. The strips also may be perforated, if desired. The exact form of wrapping used, of course, is not critical. In certain instances, the provision of more than one layer of the sheeting may be desirable, and, as is evident, the wrapping chosen in these cases should be such that the additional layers will not interfere with any fastening means which may be provided. Regardless of the form of the wrapping selected, its width preferably is at least one-half inch, inasmuch as the cutting of narrower seized sections of the cable is impractical.

The invention has been described in detail in the foregoing. It will be obvious to one skilled in the art, however, that many variations are possible without departure from the scope of the invention. We intend, therefore, to be limited only by the following claims.

We claim:

1. A method of preparing seized metal-stranded cable which comprises wrapping flexible thin metal sheeting around the section of the cable to be seized, substantially surrounding said wrapping with a charge of detonating explosive, and initiating said explosive.

2. A method of preparing seized metal-stranded cable which comprises wrapping flexible metal sheeting 5-35 mils in thickness around the section of the cable to be seized, substantially surrounding said Wrapping with a charge of detonating explosive, and initiating said explosive.

3. A method according to claim 2, wherein a layer of modifying material is provided between the wrapping and the explosive charge, said material modifying the forces generated by the detonation of the explosive.

4. A method according to claim 2, wherein the detonating explosive is in cordlike form.

5. A method according to claim 2, wherein the wrapping is of perforated sheet metal.

6. A method according to claim 2, wherein each end of the wrapping is rolled to form a hook-like member, said members being oppositely directed and interlocking.

7. A method according to claim 2, wherein a plurality of prongs are formed in one end of the wrapping, said prongs being parallel to the longitudinal axis of the wrapping and interconnecting with corresponding slots provided in the other end of the wrapping.

8. A method according to claim 2, wherein one end of the wrapping is tapered, said tapered portion of the wrapping interconnecting With one of a series of slits formed in the other end of the wrapping, said slits being perpendicular to the longitudinal axis of the wrapping.

9. A method of preparing seized metal-stranded cable which comprises wrapping flexible metal sheeting 5-35 mils in thickness around the section of the cable to be seized, said metal sheeting being selected from the group consisting of aluminum, copper, and steel sheeting, substantially surrounding said wrapping with a charge of detonating explosive, and initiating said explosive.

References Cited in the file of this patent UNITED STATES PATENTS 1,769,001 Starrett July 1, 1930 2,415,814 Davis et a1 Feb. 18, 1947 

1. A METHOD OF PREPARING SEIZED METAL-STRANDED CABLE WHICH COMPRISES WRAPPING FLEXIBLE THIN METAL SHEETING AROUND THE SECTION OF THE CABLE TO BE SEIZED, SUBSTANTIALLY SURROUNDING SAID WRAPPING WITH A CHARGE OF DETONATING EXPLOSIVE, AND INITIATING SAID EXPLOSIVE. 